1. It’s an adverb which means: ” by the the most direct route.”

2. Whereas beeline is a noun which means: “the most direct route.”

3. Collective noun for bees: colony

Collective nouns for crows:

A horde of crows

A hover of crows

A flock of crows

A parliament of crows

A murder of crows

A storytelling of crows

A pack of crows

A mob of crows

A muster of crows

Source: BirdSpot, Google and vocabulary.com